Leak detection methods have been developed to analyze fluid systems (e.g., climate control systems such as heating, cooling, ventilating, and air conditioning systems, hydraulics, engine oil systems, automatic transmission systems, fuel systems, brake systems, or radiator coolant systems) using dyes. Some methods operate by adding emissive substances (e.g., fluorescent or phosphorescent dyes) to the refrigerants and/or lubricants of the fluid system. Suitable dyes include naphthalimide, perylene, thioxanthane, coumarin, or fluorescein, and derivatives thereof. Leaks can be detected by observing fluorescence of the dye at leak sites resulting from excitation of the dye with a light source having particular illumination characteristics (e.g., wavelength or intensity). Examples of leak detection methods are described in U.S. Pat. Nos. 5,357,782 and 5,421,192 which issued to Richard G. Henry on Oct. 25, 1994, and Jun. 6, 1995, respectively, both of which are assigned to the same assignee as the assignee of the present application. Similar fluorescence methods can be used in the non-destructive testing industry.
In the field of leak detection, crack detection, and related non-destructive testing, different dyes can be utilized which fluoresce at different wavelengths. Fluorescence is the emission of light at wavelengths greater than the wavelength of light emitted from the light source used to probe for leaks.
Suitable light sources for use in fluorescence detection emit light of wavelengths suitable to excite the dye and cause light emission. The visibility of the fluorescence from the dye can be increased when the leaks are illuminated with light having a wavelength between 300 and 700 nanometers. In general, the dyes fluoresce brightly when excited by light sources which emit light in the 300 to 500 nanometer range.
Typical light sources used in these types of applications include alternating current lamps operating on either 110 to 220 volts, such as the PAR 38, manufactured by Phillips. These lamps had power outputs in the 100 to 200 watt range and produced a substantial amount of light outside of the wavelength range desired to produce a good fluorescence signal. These lamps also tend to create a large amount of heat and required the use of a ballast which provided additional bulk and weight. Self-ballasted lamps were also developed that generally had relatively long warm-up periods and were very sensitive to voltage surges.